Detailed Explanation for this Vulnerability Test
The remote host is affected by the vulnerability described in GLSA-200611-05
(Netkit FTP Server: Privilege escalation)

Paul Szabo reported that an incorrect seteuid() call after the chdir()
function can allow a possible hacker to access a normally forbidden
directory, in some very particular circumstances, for example when the
NFS-hosted targetted directory is not reachable by the client-side root
user. Additionally, some potentially exploitable unchecked setuid()
calls were also fixed.

Impact

A local attacker might craft his home directory to gain access through
ftpd to normally forbidden directories like /root, possibly with
writing permissions if seteuid() fails and if the ftpd configuration
allows that. The unchecked setuid() calls could also lead to a root FTP
login, depending on the FTP server configuration.